Citabria ACA Factory Metal Spar Wings, Champ/Citabria/Decathlon

[Bartman]

Find everything you need to know here;
https://www.americanchampionaircraft.com/retrofit-metal-spar-wings.html

From the ACA website;
Traditionally the Champion line of aircraft used wooden wing spars nailed to aluminum ribs as the primary wing structure. This changed in 1990 when American Champion Aircraft redesigned and certified this structure with aluminum spars. This change is the core difference between new aircraft and older models (1980 and older). In fact, American Champion has never offered a wood spar wing.

The metal spar wings can retrofit to any of the older Citabria line and offer an affordable alternative (and upgrade) to rebuilding an old pair of wings.

Why metal spar wings? For one, you don't see the rest of industry using wood spars. With the redesign, certain engineering aspects could be taken into account to improve performance and reliability. The metal wing assemblies act more as an upgrade than a replacement, offering numerous advantages to the owner.

Additional information at the website includes pricing, engineering justification for metal spar wings, owners' basis for the decision, and a list of FAQ's.

 

[Bob Turner]

Why did they choose the style that requires wing removal to change the windshield?

 

[rjgritter]

Why did they choose the style that requires wing removal to change the windshield?

I'm not sure about everyone else, but my experience with the fully-removable wing-root fairings has been poor. They seem to be a sloppy fit and they move around a lot in aerobatics - the upper forward portion of the fairings lifts away from the windshield in positive G's. The new style where the upper fairing is integral to the wing is much cleaner, no doubt lower drag and eliminates that flexibility.

 

[aero-pilot]

If an FAA inspector comes asking... what approval process shows the new metal spar retro fit wings are legal? I understand there is no STC issued for these retro fit wings.

 

[Big Ed]

Metal wings are in the Type Certificate, so you are bringing the aircraft into compliance with the current TCDS.

 

[aero-pilot]

here is the official response I got from ACA...

Per American Champion Aircraft drawing 7-1520 Current Rev.I dated 6-04-20 Installation Wings and Struts model 8KCAB,P/N 7-1521-1,-2,-3,and -4 wings covered are approved for installation on model 8KCAB (Metal Spar Wings).

Per RevC dated 10-14-91 (Change to metal spar wing) American Champion Drawing 7-1520.
This information is called out in the aircraft type certificate A21CE current Rev. 16 dated 01/08/2013. (See Note 8).

A FAA form 337 should be done due to the gross weight change and this being a major change.

 

[Bob Turner]

Um -

an alteration not listed in the aircraft, aircraft engine, or propeller specifications -

(1) That might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness; or

(2) That is not done according to accepted practices or cannot be done by elementary operations.


That is from 14 cfr 1.1. It is the law. The first sentence says flat out that major "changes" (alterations) are those not in the type certificate data sheets.
I did not research whether swapping wings was a major repair - a major repair does require a 337.

 

[Bob Turner]

Here is the major repair definition:

Major repair:

(1) That, if improperly done, might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness; or

My "paste" dropped the part about elementary operations. I think there is wiggle room here, but I rarely see 337s that state "remove and replace . . ."

 

[aero-pilot]

according to those definitions, I would have to agree this is a major repair.

Does anyone have a sample 337 form for the approval of the metal wings? I have asked ACA for one but they have not delivered yet... They maybe hesitant to do so. I would think a 337 is top secrete but I don't know.

 

[Bartman]

Well this flies in the face of a lot of what has been said around here regarding 337's vs. logbook entries for alterations that are done per the terms of the TCDS. For example, it's looking like an engine hp upgrade (150hp Decathlon to 180 hp Super Decathlon) actually requires a 337 where we might have said it's only a logbook entry per the TCDS, no? It affects W&B, performance, flight characteristics, etc.

 

[Big Ed]

I am sometimes reminded of Harry Truman's response when asked what he wanted for Chrismas: "a one armed economist." Thing about it for a bit.

But IMO, for a metal wing conversion, I would make a serious effort to get that done at the factory. Not because it's particularly difficult, but because you will be 100% that both the paperwork and the rigging is correct.

Anyone know what the factory labor charge is for a wing install?

 

[Bartman]

All of the info for the different models is at the ACA website

Metal Spar Wings | American Champion Aircraft

Traditionally the Champion line of aircraft used wooden wing spars nailed to aluminum ribs as the primary wing structure. With the redesign of metal spar wings, certain engineering aspects could be taken into account to improve performance and reliability.

www.americanchampionaircraft.com

 

[Big Ed]

The price sheet says "call for a quote" on install.

 

[Bartman]

huh, it does, doesn't it. sorry about that.

 

[Bob Turner]

My point was that if it is on the type certificate it is not a major alteration - by law! The law says it is not!
That should be clear.

As far as changing weight and balance - the interpretation is that the change must be to the envelope!
That is, if it just adds 20 lbs to the empty weight, without driving you out of the envelope, it is not major.
Now, major repair? You are not repairing anything when you unbolt a wing and bolt another on.

Finally, my e-mail keeps getting a note when somebody posts to this thread. How do I turn that off?

 

[Bob Turner]

Related topic - I have seen corrosion problems with these wings. First, the lift strut attach fittings disintegrated. Now we have found corrosion in the leading edge aluminum underneath the fabric. I have seen that on two different metal spar ACA products.

My J3 has the original 1946 factory leading edges, and has been parked outside for at least 25 of the last 60 years, with zero wing corrosion. Zero! And the metal spar wings sre by definition younger than that -

So what gives? Inferior aluminum?

 

[Bartman]

Finally, my e-mail keeps getting a note when somebody posts to this thread. How do I turn that off?

bob, scroll up to the top right corner of the posts on the page. there will be a small box that says "Unwatch", click on it and it will unsubscribe you from the thread and you'll stop getting notifications for every new post.

 

[Bartman]

Related topic - I have seen corrosion problems with these wings. First, the lift strut attach fittings disintegrated. Now we have found corrosion in the leading edge aluminum underneath the fabric. I have seen that on two different metal spar ACA products.

My J3 has the original 1946 factory leading edges, and has been parked outside for at least 25 of the last 60 years, with zero wing corrosion. Zero! And the metal spar wings sre by definition younger than that -

So what gives? Inferior aluminum?

i don't know but it's weird.

 

[Hiperbiper]

Well this flies in the face of a lot of what has been said around here regarding 337's vs. logbook entries for alterations that are done per the terms of the TCDS. For example, it's looking like an engine hp upgrade (150hp Decathlon to 180 hp Super Decathlon) actually requires a 337 where we might have said it's only a logbook entry per the TCDS, no? It affects W&B, performance, flight characteristics, etc.

Just because something is listed on the TCDS does not mean you can mix and match parts any time you want to...
My 7ac has many things listed as options on the -759 TCDS. There are also lots of things listed for other models in the 7 series. The 7ECA is listed there. That doesn't mean I can put anything I want from a 7eca on my 7ac.
Having something from a later model airframe in the same series can be a big help getting upgrades approved but that in and of itself is not approved data.
Changing a wing out with another wing of like form and construction? Logbook entry.
Changing a wing out with a wing using different materials, differing weights, etc. is a major change requiring a 337.

Chris

 

[Bob Turner]

So do you cite the type certificate as approved data, or get a field approval? Wouldn't those be the alternatives?

I agree - going from one model to another without converting the entire aircraft might not work, but within the model (8KCAB, for instance) if an alteration is on the type certificate, it is by definition not a major alteration.